Assembly and method for injecting a gaseous combustion agent

ABSTRACT

An assembly for injecting a gaseous combustion agent into a combustion zone, the assembly having a chamber having an inlet, through which the agent is introduced into the assembly; at least one primary injector configured to convey a primary flow of the agent from the chamber toward the combustion zone, at least one secondary injector for conveying a secondary flow of the agent from the chamber toward the combustion zone, a pressure detector; a regulating; and a control system connected to the pressure detector and to the regulating system, the control system controlling the regulating system so that the flow section of the at least one secondary passage is regulated as a function of the pressure or of the variation in pressure detected by the pressure detector.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a 371 of International Application No.PCT/EP2019/082987, filed Nov. 28, 2019 which claims priority to EuropeanPatent Application No. 18306820.4, filed Dec. 18, 2018, the entirecontents of which are incorporated herein by reference.

BACKGROUND

The present invention relates to an assembly for injecting a gaseouscombustion agent into a combustion zone, a burner comprising such anassembly and the use of such an assembly/burner in a combustion method.

In industrial combustion methods, for example, in order to transform aload (melting, heating, recycling furnace, etc.), certain flamecharacteristics are sought, in particular a flame shape and lengthadapted to the combustion chamber and/or to the load intended to beheated, in order to obtain a determined thermal transfer profile and tooptimize the production quality and the lifetime of the equipment.

The flame characteristics are particularly determined by the nature ofthe combustion agents (fuel and oxidant) and how they are introducedinto the combustion zone (flows, speeds, space distribution, etc.).

Thus, a burner is known from EP-A-0763692 that comprises a firstinternal passage for supplying oxygen-rich oxidant (at least 80% O₂), anintermediate passage for supplying fuel externally surrounding the firstoxidant supply passage and a second external passage for supplyingoxidant externally surrounding the passage for supplying fuel. Accordingto EP-A-0763692, the burner comprises a means for varying the flow rateof oxidant injected through the first internal passage, this allows acharacteristic of the flame, such as the flame length and theluminosity, to be controlled.

Similarly, the use of a burner is known from EP-A-1016825 that comprisesa first internal passage for supplying oxidant, an intermediate passagefor supplying fuel externally surrounding the first oxidant supplypassage and a second external oxidant supply passage externallysurrounding the fuel supply passage for heating a molten glass transferchannel during glass production and for regulating the flame lengthgenerated by means of said burner by modifying the proportion of thetotal flow of oxidant passing through the first oxidant supply passage.

The aforementioned burners are burners with concentric and adjacentinjection of fuel and oxidant generating a flame with an essentiallycircular cross-section.

Other burners generate flames called “flat flames” and/or inject atleast some of the oxidant at a distance from the injection of the fuel,and even inject at least some of the fuel at a distance from theinjection of the oxidant.

Thus, EP-A-2143999 describes a burner comprising:

-   -   at least two gaseous fuel passages;    -   at least one oxidant passage; and    -   at least one outlet surface, in which the at least one gaseous        fuel passage or the at least one oxidant passage terminate.

This known burner also comprises:

-   -   means capable of supplying an oxidant flow, as well as means for        injecting said oxidant flow into the at least one oxidant        passage; and    -   means capable of supplying at least one flow of gaseous fuel, as        well as means for injecting this flow of gaseous fuel into the        at least two gaseous fuel passages,        in order to generate at least one oxidant jet and at least two        gaseous fuel jets that meet in a combustion zone downstream of        the burner.

According to EP-A-2143999, the at least two gaseous fuel passages eachcomprise an internal passage and a coaxial external passage.

A means for controlling the flow of gaseous fuel regulates the flow ofgaseous fuel respectively through the internal passages and the externalpassages by means of a gaseous fuel distributor.

This allows both the thermal transfer profile and the flame length to becontrolled.

If it is thus known that it is possible to modify certaincharacteristics, and in particular the generated flame length, byadjusting the distribution of the flow of fuel or of oxidant on aplurality of concentric passages/injectors, the known burners do notcomprise any feedback means allowing the operation of the burner, andtherefore the targeted characteristic of the flame, to be adjusted inreal time.

Surprisingly, it has now been discovered that it is possible to producesuch a feedback system on the basis of a detected pressure of thegaseous combustion agent before it is distributed.

Summary

The present invention relates to an assembly for injecting a gaseouscombustion agent into a combustion zone, which gaseous combustion agentis selected from gaseous fuels and gaseous oxidants.

The assembly comprises a chamber and the agent is introduced into theassembly via an inlet of this chamber.

The assembly comprises at least one primary injector for conveying aprimary flow of the agent from the chamber toward the combustion zoneand for injecting said primary flow into the combustion zone. To thisend, the at least one primary injector is fluidly connected to thechamber by means of at least one passage, called primary passage.

The assembly also comprises at least one secondary injector forconveying a secondary flow of the agent from the chamber toward thecombustion zone and for injecting said secondary flow into thecombustion zone. The at least one secondary injector is in turn fluidlyconnected to the chamber by means of at least one passage, calledsecondary passage. The at least one secondary passage has an adjustableflow section.

A regulating system, for example, in the form of a valve, allows thisflow section of the at least one secondary passage to be regulated.

The assembly also comprises a pressure detector for detecting a pressureor a variation in gas pressure in the chamber, as well as a controlsystem connected to the pressure detector.

The control system is also connected to a system for regulating andcontrolling said regulating system, so that the flow section of the atleast one secondary passage is regulated as a function of the pressureor of the variation in pressure detected by the pressure detector of theassembly.

According to one embodiment, the control system, which can be ananalogue or digital control system, is adapted to control the regulatingsystem so that the gas pressure in the chamber is located in apredetermined pressure zone by regulating the flow section of the atleast one secondary passage.

According to another embodiment, the control system is adapted tocontrol the regulating system so that the gas pressure in the chambercorresponds to a value that is predetermined by regulating the flowsection of the at least one secondary passage.

It is to be noted that the zone or predetermined pressure range can beconstant over time, but that it can also vary over time, for example:

-   -   as a function of the steps of the method such as, for example, a        melting method or a heating method, in which the assembly is        used, which method can be cyclical or non-cyclical;    -   as a function of the power required in the combustion zone; or    -   as a function of a feedback parameter other than the pressure in        the chamber of the assembly.

The above statements are also applicable to the predetermined value ofthe gas pressure.

As indicated above, the system for controlling the assembly can be ananalogue or digital system. It can be mechanical, for example, pneumaticor hydraulic. Preferably, the control system is digital. According to apreferred embodiment, the control system is programmable. In this case,in order to implement the injection assembly according to the invention,the control system is programmed so as to control the regulating systemso as to activate the regulating system as a function of the pressure orof the variation in pressure detected by the pressure detector. The gaspressure or the variation in gas pressure detected by the pressuredetector is then transferred to the programmable control system: forexample, by means of a wired connection or by means of a wirelessconnection.

The regulating system can comprise various means for regulating the flowsection of the at least one secondary passage, such as one or moreadjustable valves positioned in the at least one secondary passagebetween the chamber and the at least one secondary injector, or themovement of a mechanical element acting as a valve for the at least onesecondary passage, with this movement being generated, for example, bytranslation, by rotation (screwing) or by deformation of a mechanicalelement connected to the valve or even by modifying the magnetic stateof a metal element.

According to a simple and reliable embodiment, the regulating system isprovided with at least one valve capable of regulating the flow sectionof the at least one secondary passage by at least partially pluggingsaid passage.

Such a regulating system can particularly assume the following form. Theat least one secondary passage fluidly connecting the at least onesecondary injector to the chamber has an internal surface in the form ofa funnel and the regulating system comprises a valve with acorresponding external surface and that can be moved along thelongitudinal axis of the secondary passage. When the valve is thus movedalong said longitudinal axis, the external surface of the valve movestoward or away from the internal surface of the secondary passage andthe flow section of said passage is respectively reduced or enlarged.

It is also to be noted that it can be advantageous for the regulatingsystem to be designed so that the flow section of the at least onesecondary passage is never fully closed. Indeed, in order to providesufficient cooling for the at least one secondary injector, and/or toavoid clogging the at least one secondary injector (for example, due todeposits of condensable substances present in the atmosphere of thecombustion zone or due to the formation of soot originating from theoverheating of the gaseous fuel in contact with at least one secondaryinjector), a minimal gas flow through the at least one secondaryinjector can be necessary. However, it is also possible to contemplatethat such a minimal gas flow is ensured using means other than theregulating system defined above such as, for example, fluid passagesthat short-circuit the valve and that are small so as to simply ensurethis minimum flow.

The assemblies are typically made from metal, with the injectors, or atleast the downstream ends (injection ends), often advantageously beingmade of high heat and oxidation resistant metals, such as Inconel® typenickel-chromium austenitic steel alloys or Kanthal® type nickel-freealloys.

The assembly according to the invention can more specifically compriseat least one pair of a primary injector with a secondary injector, inwhich pair one from among the primary injector and the secondaryinjector surrounds the other one from among the primary injector and thesecondary injector.

The primary injector thus can surround the secondary injector or thesecondary injector can surround the primary injector of the pair.

According to an advantageous embodiment, the primary injector of thepair is surrounded by the secondary injector of the pair.

According to a particular embodiment, the primary injector and thesecondary injector of the pair are concentric. However, in some cases, anon-concentric arrangement can be useful.

It is to be noted that such a configuration in pairs does not excludethe presence of other elements, and in particular the presence of one ormore other injectors in or around either one of the injectors of thepair.

For example, according to a particular embodiment, the fluid can be agaseous oxidant, such as a gas containing at least 80 vol %, andpreferably at least 90 vol %, of oxygen. The primary injector of thepair is located at the center and is surrounded by the secondaryinjector of the pair, preferably concentrically. An injector forinjecting fuel into the combustion zone is located between the primaryinjector and the secondary injector of the pair, so that the fuelinjector surrounds the primary oxidant injector and is surrounded by thesecondary oxidant injector, the assembly thus forms part of a burner forthe combustion (at least partial) of the fuel with the oxidant, andwherein the flow section of the secondary injector, and therefore alsothe distribution of the oxidant between the primary flow and thesecondary flow, are regulated by the control system by means of theregulating system as a function of the gas pressure or the variation ingas pressure in the chamber of the assembly detected by the pressuredetector.

According to another similar embodiment, the fluid is a gaseous fuel,such as natural gas. The primary injector of the pair is located at thecenter and is surrounded by the secondary injector, preferablyconcentrically. An injector for injecting oxidant into the combustionzone is located between the primary injector and the secondary injectorof the pair, so that the oxidant injector surrounds the primary fuelinjector and is surrounded by the secondary fuel injector. The oxidantpreferably is a gas containing at least 80 vol %, and more preferably atleast 90 vol %, of oxygen. The assembly thus forms part of a burner forthe combustion (at least partial) of the fuel with the oxidant, andwherein the flow section of the secondary injector, and therefore alsothe distribution of the fuel between the primary flow and the secondaryflow of fuel, are regulated by the control system by means of theregulating system as a function of the gas pressure or the variation ingas pressure in the chamber of the assembly detected by the pressuredetector.

The assembly according to the invention can comprise a single primaryinjector and a single secondary injector, and in particular a singlepair of a primary injector with a secondary injector.

According to an alternative embodiment, the assembly according to theinvention comprises a plurality of primary injectors and/or a pluralityof secondary injectors, and in particular a plurality of pairs of aprimary injector with a secondary injector.

According to a particular embodiment, the at least one secondaryinjector of the assembly is spaced apart from the at least one primaryinjector of the assembly, without the at least one primary injector ofthe assembly surrounding a secondary injector of the assembly andwithout the at least one secondary injector of the assembly surroundinga primary injector of the assembly.

In this case, the at least one primary injector can particularly extendinto a first plane, whereas the at least one secondary injector extendsinto a second plane, with the second plane being parallel to the firstplane. In this way it is possible to inject the primary flow and thesecondary flow of the gaseous combustion agent into the combustion zonealong two parallel planes.

According to an alternative embodiment, the at least one primaryinjector extends into a first plane and the at least one secondaryinjector extends into a second plane, with the first plane and thesecond plane intersecting downstream of said primary and secondaryinjectors, i.e. inside the combustion zone into which the gaseouscombustion agent is injected.

The assembly according to the invention can comprise at least twoprimary injectors and/or at least two secondary injectors, preferably atleast two primary injectors and at least two secondary injectors. Thisis particularly advantageous in the case whereby, as described above,the at least one primary injector extends into a first plane and the atleast one secondary injector extends into a second plane different fromthe first plane.

In order to inject gaseous agent into the combustion zone, the inlet ofthe assembly, which is also the inlet of the chamber of the assembly, isfluidly connected to a gaseous fuel source, preferably a gaseous fuelsource selected from natural gas, biogas, propane, butane, the residualgases of steel-making or methane-reforming methods, hydrogen, anymixture of said gaseous fuels, or is fluidly connected to a gaseousoxidant source, preferably with an oxygen content of 21 to 100 vol %,preferably greater than 21 vol %, and in particular at least 80 vol %,more preferably at least 90 vol %.

Such a source can be a tank of the gaseous agent in gaseous form or inliquefied form, a supply duct conveying said gaseous agent or agenerator of said gaseous agent.

The invention also relates to an installation comprising a plurality ofassemblies according to any one of the embodiments described above. Inthis case, it can be preferable for this installation to comprise acommon control system that is capable of controlling, preferablyindependently, the system for regulating each assembly of theinstallation as a function of the gas pressure or the variation in gaspressure detected by the pressure detector of said assembly.

As indicated above, the assembly can be incorporated in a burner.

Such a burner according to the invention therefore comprises an assemblyaccording to any one of the aforementioned embodiments for injecting agaseous combustion agent into a combustion zone, which gaseouscombustion agent is selected from a gaseous fuel and a gaseous oxidant.

Such a burner typically also comprises at least one additional injectorfor injecting an additional fluid into the combustion zone. As a generalrule, when the gaseous agent injected by the assembly is a gaseous fuel,the at least one additional injector is adapted for injecting a gaseousoxidant into the combustion zone, and when the gaseous agent injected bythe assembly is a gaseous oxidant, the at least one additional injectoris adapted for injecting a fuel (gaseous or non-gaseous) into thecombustion zone.

According to one embodiment, the burner comprises a block with an inletface and an outlet face opposite the inlet face. The combustion zone islocated downstream of the outlet face.

Contrary to the assembly, the block is typically made from a refractorymaterial, such as cement, or an electrofusion type material, or apressed material, mainly made up of alumina and/or zirconium and/orsilica and/or magnesia or a mixture of these components in variedproportions as a function of the application method.

The assembly is then attached to the inlet face of the block so that theinjectors of the burner, and therefore also the injectors of theassembly, are positioned in one or more perforations that pass throughthe block from the inlet face to the outlet face.

Thus, a burner according to the invention can, for example, comprisesuch a block with one or more first perforations, which terminate at afirst level in the outlet face of the block, as well as one or moreadditional perforations, which terminate in the outlet face at a secondlevel located below or above the first level. The assembly comprises atleast two, and preferably at least three, primary injectors andsecondary injectors for conveying and injecting gaseous fuel into thecombustion zone. Each of the primary injectors forms a pair with one ofthe secondary injectors. According to one embodiment, each of theprimary injectors surrounds one of the secondary injectors. According toa preferred embodiment, each of the secondary injectors surrounds one ofthe primary injectors. These pairs, for example, in triplicate, arepositioned in the one or more first perforation(s) that terminate at thefirst level. The burner also comprises a plurality of additionalinjectors for conveying and injecting oxidant into the combustion zone.Said additional injectors are positioned in the one or more additionalpassages of the block so as to allow oxidant to be injected into thecombustion zone above or below the gaseous fuel. The additionalinjectors can extend into a plane parallel to the plane of the pairs ofa primary injector with a secondary injector. According to anotherembodiment, the additional injectors can define an injection plane forthe oxidant that intersects the plane of the pairs in the combustionzone downstream of the outlet face where the oxidant injected by theadditional injectors mixes and reacts with the fuel injected by thepairs.

As already indicated above, other, and in particular one or moreinjector(s) other than the primary injector and the secondary injectorof the pair, can be present in or around either one from among theprimary injector and the secondary injector of the pair.

According to a first embodiment, the one or more additional passage(s)terminate in the outlet face of the block above the one or more firstpassage(s). According to another embodiment, the one or more additionalpassage(s) terminate in the outlet face of the block below the one ormore first passage(s).

According to a third embodiment, the block comprises one or moreadditional passage(s), which terminate in the outlet face at a levellocated above the first level and in which at least two, and preferablyat least three, additional injectors for the oxidant are located, aswell as one or more additional passage(s), which terminate in the outletface of the block below the first level and in which at least two, andpreferably at least three, additional injectors for the oxidant are alsolocated. This embodiment allows, according to the requirements of themethod, oxidant to be injected into the combustion zone above, below orabove and below the gaseous fuel.

The invention also relates to a furnace comprising an internalcombustion zone and equipped with at least one assembly according to theinvention for injecting a gaseous combustion agent into said combustionzone, which gaseous combustion agent is selected from gaseous fuels andgaseous oxidants. As indicated above, the at least one assembly can formpart of a burner according to the invention, in which case the furnaceis equipped with at least one burner according to the invention.

The present invention particularly advantageously can be implemented ina furnace selected from furnaces for manufacturing or heating glass orenamels, furnaces for manufacturing or recycling or heating metals, suchas rotary furnaces, or reverberatory furnaces for aluminum, copper orlead, cast iron, steel, etc.

Another aspect of the present invention is a combustion method, in whicha gaseous combustion agent is injected into a combustion zone by meansof an assembly according to the invention, which gaseous combustionagent is selected from gaseous fuels and oxidants, said assembly beingable to form part of a burner according to the invention.

According to this method, the pressure detector of each assembly detectsthe gas pressure or a variation in the gas pressure in the chamber ofthis assembly, the system for regulating the assembly regulates the flowsection of its at least one secondary passage, and the control systemcontrols the regulating system so that the flow section of the at leastone secondary passage of each assembly is regulated as a function of thepressure or of the variation in pressure detected by the pressuredetector of this assembly.

As already described above within the context of the installation and ofthe furnace according to the invention, in the case whereby a pluralityof assemblies is used in the method, each assembly can have its owncontrol system connected to the pressure detector and to the regulatingsystem, with the control system controlling the regulating system sothat the flow section of the at least one secondary passage is regulatedas a function of the pressure or of the variation in pressure detectedby the pressure detector of said assembly. However, in an oftenadvantageous manner, a common control system can control the system forregulating each assembly as a function of the pressure or of thevariation in pressure detected by the pressure detector of the relevantassembly.

As has also already been previously indicated, the system for regulatingthe assembly can be controlled so that the gas pressure in the chamberof the assembly is located in a predetermined pressure zone or even sothat the gas pressure in the chamber of the assembly corresponds to apredetermined value.

The gaseous combustion agent injected into the combustion zone by meansof the assembly is a gaseous fuel selected from natural gas, biogas,propane, butane, the residual gases of steel-making or methane-reformingmethods, hydrogen or any mixture of the aforementioned gases, or is agaseous oxidant, preferably with an oxygen content of 21 to 100 vol %,preferably greater than 21 vol %, and in particular at least 80 vol %,more preferably at least 90 vol %.

The method according to the invention is particularly useful forgenerating combustion inside a combustion zone within the context of amethod such as manufacturing or recycling glass or enamels,manufacturing or recycling or heating metals, such as aluminum, copper,lead, cast iron, steel, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its advantages will be better understood in the lightof the following examples: (with reference to FIGS. 1 to 5), in which:

FIG. 1 schematically shows an assembly comprising a primary injector(21) with a concentric secondary injector (22), the secondary injector(22) surrounding the primary injector (21);

FIG. 2 schematically shows an assembly comprising a primary injector(21) with a concentric secondary injector (22), the primary injector(21) surrounding the secondary injector (22);

FIG. 3 schematically shows an assembly comprising a primary injector(21) with a non-concentric secondary injector (22), separated by adistance;

FIG. 4 schematically shows a view of the assembly incorporated in aburner for injection of a gaseous combustion agent into a combustionzone (1).

FIG. 5 schematically shows a view of the assembly incorporated in aburner for injection of a gaseous combustion agent into a combustionzone (1).

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1, 2 and 3 show a fluid inlet chamber (11). The primary injector(21) is fluidly connected to the chamber (11) by means of a primarypassage (23). The secondary injector is fluidly connected to the chamber(11) by means of a secondary passage (24). The secondary passage (24)has an adjustable flow section. A regulating system (32) allows thisflow section of the secondary passage (24) to be regulated by virtue ofa valve (33).

FIGS. 1, 2 and 3 also show a pressure detector (30) for detecting a gaspressure or a variation in gas pressure in the chamber (11), as well asa control system (31) connected to the pressure detector (30). Thecontrol system is also connected to and controls the regulating system(32).

FIG. 4 schematically shows an assembly comprising three primaryinjectors (21) each surrounded by its concentric secondary injector(22), and a chamber (11).

The primary injectors (21) are fluidly connected to the chamber (11) bythe primary passages (23). The secondary injectors (22) are fluidlyconnected to the chamber (11) by the secondary passages (24). Thesecondary passage has an adjustable flow section. A regulating system(32) allows this flow section of the secondary passage (24) to beregulated by virtue of a valve (33). A pressure detector (30) is presentfor detecting a pressure or a variation in gas pressure in the chamber(11). A control system (31) is connected to the pressure detector (30).This control system is also connected to and controls the regulatingsystem (32).

In FIGS. 4 and 5, the burner comprises a block (40) with an inlet face(41) and an outlet face (42) opposite the inlet face, as well asadditional injectors (50) for injecting an additional fluid into thecombustion zone (1).

The automatic regulation by the feedback system according to the presentinvention advantageously can be implemented in various combustionmethods, such as for glass production.

The glass production furnaces mainly use air preheated to over 1000° C.as an oxidant. This hot air is obtained by passing through regenerators(stack of refractory bricks). The amount of oxidant injected into thefurnace at this temperature level involves a significant amount ofmovement.

During the campaign of a furnace, production may need to be increasedbeyond the capacity of the regenerators, which cannot provide a greateramount of hot air due to the limitation of the draw of the fans. Asimilar problem occurs when the state of the bricks does not allow or nolonger allows the desired preheating temperatures to be obtained.

The burner installation operating with an oxygen-rich oxidant(oxy-burner) then appears to be a particularly suitable solution. Theseburners are generally installed in the openings available dose to theregenerators. With the oxy-combustion (i.e. combustion with an oxidantcontaining at least 80 vol %, and preferably at least 90 vol %, ofoxygen) generating an amount of smoke that is 4 times lower than aircombustion and with at least equivalent efficiency, the flamesoriginating from oxy-burners, hereafter called “oxy-flames”, areseverely disrupted by the flames, called “aero-flames”, originating fromregenerators operating with hot air, due to the lower amount of movementof the oxy-flames. These disruptions can lead to the oxy-flameinterfering with the molten solid material and unburnt materials andthus to glass quality or energy efficiency problems. These problems areeven more significant when the power (and therefore the flows of thecombustion agents) of the oxy-burners is reduced for lower increasedproduction phases. It is therefore essential to maximize the pulse orthe amount of movement of the oxy-flames throughout the entire powerrange of the oxy-burners.

Systems, such as those described in document EP 2143999, allow manualregulation of the flow of gaseous fuel between two injections (primaryand secondary) in order to maximize the pulse of the fuel and thusensure the stability of the flame of the oxy-burner. However, thesemanual systems require constant adjustment of the fluid distribution bythe operators, without being able to easily assess the impact of theseadjustments on the method in real-time. In order to avoid theseadjustments and any quality problems, the operators most often adjustthe power on the air burners (regenerator), causing excessive oxygenconsumption and an increase in the production costs.

The present invention advantageously can be used in this case bydefining a predefined pressure range or a predefined pressure allowingautomatic distribution to be ensured of the flow between the primary andsecondary injections, so as to maximize the pulse of the oxy-flameirrespective of the total flow of fuel,

For example, in the case of a 4% production increase, the power of anoxy-burner can be 800 kW, whereas for an 8% oxygen increase, the powerof an oxy-burner can be 1.8 MW. It has been determined that a pressureof 300 mbarg in the distribution chamber between the two fuel injectionsallows a highly stable flame to be provided both at 800 kW and at 1800kW. The automatic regulation, according to the invention, of thedistribution of the fuel, as a function of the gas pressure in thechamber when the power varies, will thus allow the production costs tobe optimized, quality defects to be limited and energy consumption to beoptimized.

It will be understood that many additional changes in the details,materials, steps and arrangement of parts, which have been hereindescribed in order to explain the nature of the invention, may be madeby those skilled in the art within the principle and scope of theinvention as expressed in the appended claims. Thus, the presentinvention is not intended to be limited to the specific embodiments inthe examples given above.

1.-15. (canceled)
 16. An assembly for injecting a gaseous combustion agent into a combustion zone, which gaseous combustion agent is selected from gaseous fuels and gaseous oxidants, the assembly comprising: a chamber comprising an inlet, through which the agent is introduced into the assembly; at least one primary injector configured to convey a primary flow of the agent from the chamber toward the combustion zone and for injecting said primary flow into the combustion zone, said at least one primary injector being fluidly connected to the chamber by means of at least one primary passage; at least one secondary injector for conveying a secondary flow of the agent from the chamber toward the combustion zone and for injecting said secondary flow into the combustion zone, said at least one secondary injector being fluidly connected to the chamber by means of at least one secondary passage; a pressure detector for detecting a gas pressure or a variation in gas pressure in the chamber; a regulating system for regulating a flow section of the at least one secondary passage; and a control system connected to the pressure detector and to the regulating system, the control system controlling the regulating system so that the flow section of the at least one secondary passage is regulated as a function of the pressure or of the variation in pressure detected by the pressure detector.
 17. The assembly as claimed in claim 1, wherein the control system is configured to control the regulating system so that the gas pressure in the chamber is located in a predetermined pressure zone or so that the gas pressure in the chamber corresponds to a value that is predetermined by regulating the flow section of the at least one secondary passage.
 18. The assembly as claimed in claim 1, wherein the regulating system is provided with at least one valve configured to regulate the flow section of the at least one secondary passage.
 19. The assembly as claimed in claim 1, comprising at least one pair of a primary injector with a secondary injector, in which pair one from among the primary injector and the secondary injector surrounds the other one from among the primary injector and the secondary injector.
 20. The assembly as claimed in claim 1, comprising at least two primary injectors and/or at least two secondary injectors.
 21. An installation comprising a plurality of assemblies as claimed in claim 1, the installation comprising a common control system that is connected to the pressure detector of each assembly and that is configured to control the regulating system of each assembly as a function of the gas pressure or of the variation in gas pressure detected by the pressure detector of said assembly.
 22. A burner comprising an assembly as claimed in claim 1 for injecting a gaseous combustion agent into a combustion zone, which gaseous combustion agent is selected from a gaseous fuel and a gaseous oxidant, and at least one additional injector for injecting an additional fluid into the combustion zone.
 23. The burner as claimed in claim 22, comprising a block with an inlet face and an outlet face opposite the inlet face, in which burner the assembly is attached to the inlet face of the block so that the injectors of the burner are positioned in one or more perforations passing through the block of the inlet face to the outlet face.
 24. The burner as claimed in claim 23, wherein the primary and secondary injectors of the assembly form pairs of a primary injector with a secondary injector, the pairs being positioned in at least one first perforation of the block and the at least one additional injector being positioned in at least one additional perforation of the block.
 25. The burner as claimed in claim 24, comprising at least two pairs and at least two additional injectors, wherein the pairs define a first injection plane for the fluid and wherein the injectors define a second injection plane for the additional fluid that is different from the first plane, the second plane being parallel to the first plane or being oriented so as to intersect the first plane in the combustion zone downstream of the outlet face.
 26. A furnace comprising an internal combustion zone and comprising at least one assembly as claimed in claim 1 for injecting a gaseous combustion agent into the internal combustion zone of the furnace, which gaseous combustion agent is selected from gaseous fuels and gaseous oxidants.
 27. The furnace as claimed in claim 26 comprising a plurality of assemblies, the furnace comprising a common control system that is connected to the pressure detector of each assembly and that is configured to control the regulating system of each assembly as a function of the gas pressure or of the variation in gas pressure detected by the pressure detector of said assembly.
 28. A combustion method, wherein a gaseous combustion agent is injected into an internal combustion zone by means of an assembly as claimed in claim 1, which gaseous combustion agent is selected from gaseous fuels and oxidants, in which method: the pressure detector of the assembly detects the gas pressure in the chamber of the assembly; the system for regulating the assembly regulates the flow section of the at least one secondary passage; and the system for controlling the assembly controls the system for regulating the assembly so that the flow section of the at least one secondary passage is regulated as a function of the pressure or of the variation in pressure detected by the pressure detector of the assembly.
 29. The method as claimed in claim 28, wherein the control system controls the regulating system so that the gas pressure in the chamber is located in a predetermined pressure zone or so that the gas pressure in the chamber of the assembly corresponds to a value that is predetermined by regulating the flow section of the at least one secondary passage of the assembly.
 30. The method as claimed in claim 28, wherein the gaseous combustion agent is a gaseous fuel selected from natural gas, biogas, propane, butane, the residual gases of steel-making or methane-reforming methods, hydrogen or any mixture of at least two of these gaseous fuels, or is a gaseous oxidant with an oxygen content of 21 to 100 vol %. 